1. Technical Field
Example embodiments of the present invention relate in general to an operation method of a station (STA) in a wireless local area network (WLAN), and more particularly, to a technology for generation and transmission of a frame supporting orthogonal frequency division multiplexing access (OFDMA) in a WLAN.
2. Related Art
With the development of information and communications technology (ICT), a variety of wireless communication technologies are under development. Among them, a WLAN is a technology that makes it possible to wirelessly access the Internet at home or in companies or specific service providing areas using portable terminals, such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), a smart phone, and a tablet personal computer (PC), based on wireless frequency technology
The standards for WLAN technology are being developed as Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards. IEEE 802.11a provides a transmission rate of 54 Mbps at 5 GHz using an unlicensed band. IEEE 802.11b provides a transmission rate of 11 Mbps at 2.4 GHz using a direct sequence spread spectrum (DSSS) technique. IEEE 802.11g provides a transmission rate of 54 Mbps at 2.4 GHz by OFDM. IEEE 802.11n provides a transmission rate of 300 Mbps for four spatial streams using multiple input multiple output-OFDM (MIMO-OFDM). IEEE 802.11n supports a channel bandwidth up to 40 MHz, and in this case, provides a transmission rate of 600 Mbps.
As WLANs are widespread and applications using the same are diversified, there is an increasing necessity for a new WLAN technology to support a greater throughput than a data processing rate supported by IEEE 802.11n. Very high throughput (VHT) WLAN technology is one of the IEEE 802.11 technologies proposed to support a data processing rate of 1 Gbps or more. Among them, IEEE 802.11 ac is a standard for providing a VHT in a band of 6 GHz or less, and IEEE 802.11ad is a standard for providing a VHT in a 60 GHz band.
In addition to these, standards for a variety of WLAN technologies have been prescribed, and development of the standards is underway. Typically, IEEE 802.11af is a standard prescribed for operation of a WLAN in an unused television (TV) band (white space), IEEE 802.11ah is a standard prescribed to support a large number of terminals operating with low power, and IEEE 802.11ai is a standard prescribed for fast initial link setup (FILS) in a WLAN system. In recent years, an IEEE 802.11ax standard for improving frequency efficiency in an environment dense with a plurality of base stations and terminals is being developed.
These WLAN technologies can allow the use of wide bandwidths of 80 MHz, a maximum of 160 MHz, etc. to increase a transmission rate. However, a WLAN standard provides backward compatibility with a previous standard, and thus, during communication with a device using a narrow bandwidth, it is not possible to use a remaining bandwidth. In other words, when an access point (AP) is a WLAN device using a wide bandwidth and a STA is a WLAN device using a narrow bandwidth, the AP can simultaneously use a primary channel and a secondary channel, but the STA can use the primary channel only. Therefore, when the AP transmits data to the STA, the AP is required to use the primary channel only, and the secondary channel is not used. This problem also occurs when the STA transmits data to the AP.